Mom: "Hey! Go put your clothing on!" Kid: "But Mom, underwear is clothing!"
No. Underwear is a plural noun, you never use "an" with it, just like you don't say "a trousers".
if underwear is plural, then you should say "underwear are clothing" using "are" instead of "is "
You're right. I've edited my previous comment. You don't say "an underwear" because "underwear" is non-countable.
I found it pretty clear after learning pantalono and pijxamo that kalsono is singular. In English underwear is plural, but in Esperanto it's singular, just like pantalono is. Sxuoj and gantoj are plurals in Esperanto because they can be spoken of separatly. I suppose if you separate your pajamas, you have pijxamo cxemizo and pijxamo pantalono.
I could go for "singular or non-countable, collective."
The underwear in my drawer upstairs is all too small. I need to buy new underwear. When I do, it will be new.
Is kalsono all underwears or only for men ? I mean in France, un caleçon is an underwear for men
I'm sure usage varies. I tend to think of it as for women - but I could also imagine using it to talk about speedos for men.